Chaetognaths off Peru — • BiERl 
257 
to compare their relative abundances or ab- 
solute concentrations. 
In Figure 2 the total number of chaeto- 
gnaths found at each station is shown. At no 
station were chaetognaths absent, but at the 
southernmost station only a single specimen 
was taken. The data are highly variable and 
no general trend is evident. The day tows 
averaged four times as many chaetognaths as 
the night tows but because of the great varia- 
bility in abundance this is not regarded as 
significant. 
In Figure 3 the number of species found at 
each station is shown. Although the data are 
highly variable, a general decrease in the num- 
ber of species at the southern stations is ap- 
parent. This is due to a lack of equatorial and 
central oceanic species at the southern stations. 
Fig. 2. Number of chaetognaths taken at each sta- 
tion in May 1941. 
Fig. 3. Number of chaetognath species found at each 
station in 1941. 
Pterosagitta draco (Fig. 4),* occurred at all 
but four stations. This species, which can be 
characterized as a warm water inhabitant, is 
found throughout the Pacific except off the 
California and Korean coasts between roughly 
40 degrees north and 40 degrees south (Bieri, 
unpublished data). As might be expected, it 
does not show any marked discontinuities in 
the Peru region, but does appear to decrease 
in abundance at the southern stations. 
Krohnitta pacifica (Fig. 5) occurred at nine 
nearly consecutive stations. This species was 
absent from the inshore stations off Peru 
during August, 1952 (Shellback Expedition). 
* In Figures 4-13, the numbers refer to the number 
of specimens of the chaetognath species being dis- 
cussed which were taken in a five-minute surface tow, 
using a one-half meter net. 
